The present invention generally relates to avionics systems in commercial and military aircraft, and more specifically, to bus communications methods and systems for cooperatively sending information between embedded computers each controlling individual engines within an airframe.
Modern turbine engines are complicated devices requiring computer control to maintain their peak efficiency of operation. Data about their environment must be fed to these turbine engines and their operating parameters must be precisely adjusted in a coordinated manner. A pilot uses flight deck controls, such as throttles, to direct the operation of these turbine engines, and these directions must be communicated to computers associated with the engine to provide a coordinated change of operating variables within permissible envelopes. Modern aircraft employ a flight deck computer to serve as a communications hub for receiving the manual control inputs received from the numerous manual controls in the cockpit, determining which flight instrument is to receive the input, formatting a message with information regarding the manual input, and sending the message to the flight instrument. The engine computers are normally one of many such flight instruments on an aircraft. The engine computers in turn send status and acknowledgement messages back to the flight deck computer for displaying status and values of flight parameters.
The ARINC 429 bus is typically used for such communications. The ARINC 429 protocol was originally promulgated by Aeronautical Radio, Incorporated (ARINC) for airborne data communication between instruments and employs a unidirectional transmission of 32 bit words (messages) over two wire twisted pairs. Each word contains five fields, one of which is a message identifier, or label, identifying the data type and the parameters associated with it.
When two or more engines are carried on the airframe, each engine computer must not only interact with the flight deck computer, but it must also interact with other engine computers. Not only must the operating variables within each engine be coordinated internally, but the changes in one engine must be coordinated with the other engines as well. One problematic scenario is the situation in which one engine goes out and the others must compensate for the change in bleed air requirements and thrust. If the remaining engines are not adjusted, then they may also fail through overheating. Normally the pilot would provide control over the engines but some things may be controlled between the engines without pilot intervention.
One solution for a multi-engine aircraft involves establishing a second cross-engine communication bus dedicated for communications between the engine computers and programming the engine computers to exchange information over the communication bus. This solution allows the engine computers to communicate with each other without involvement from the flight deck computer over the ARINC 429 bus. Without such a dedicated communications bus, the pilot must manually perform the coordination activities between the engines or the coordination task must be accomplished within the flight deck computer. In general, the vendor of the flight deck computer is not necessarily the same as the vendor of the engine computers, and neither party necessarily has the expertise to support the other in this regard.
U.S. Pat. No. 5,165,240 shows a configuration of a full authority digital engine control, or FADEC, serving as an engine computer for each of two engines. The left and right FADECs communicate with each other via a RS-422 bus (36, FIG. 2), and each receives inputs from their respective engine sensors and autopilots (24L, 24R, FIG. 2), and sends display information to a common engine indication emergency crew alerting system (EICAS) (28L, 28R, FIG. 2). A first ARINC 429 communications bus provides communications with the engine sensors, and a second ARINC 429 communications bus, which may be the same as the first ARINC 429 communications bus, also provides communications with the EICAS.
U.S. Pat. No. 5,136,841 describes such an engine-to-engine communication setup, where an optical bus is provided for allowing two engine electronic control units (engine computers) to communicate with one another (FIG. 1), replacing the standard isolation station coupled with each engine electronic control unit to provide electrically isolated engine-to-engine communications. The optical couplers to an optical bus provide the necessary electrical isolation instead of the standard ARINC 429 connection. This configuration implements a special dedicated communications bus (88A, 88B, 90A, 90B) between the two engine control units (12, 14).
However, some business jets do not have existing cross-engine communication buses wired into the aircraft, which prevents engine-to-engine sharing of important data. To retrofit such a cross-engine communication bus into an existing airframe would require major maintenance and incur significant cost in terms of installation, testing, updates of schematic diagrams, new documentation, and recertification of the aircraft. Furthermore, significant aircraft downtime would be required in order to add this ability to an existing aircraft configuration.
As can be seen, there is a need for a method and apparatus to support engine-to-engine communications in an airframe in which there is no dedicated bus installed between engines. Such a capability should be relatively inexpensive and capable of implementation without excessive aircraft downtime.